Very Compact Subwoofer

I see there is also a smaller HSU Research sub; I've got some options now! Thanks, everyone, for the leads!

Douglas_schroeder, are you building it into a cabinet?

I'm very pleased with my Sunfire Super Jr, but it's a dual driver unit, so not an easy install if it's enclosed. Other than that I second the Velodyne Micro-vee series.

Don't forget MJ Acoustics and Rel for small foot prints.

Leedistad, No, I would not build these subs into a cabinet. I'll be using them standing alongside a pair of Eminent Technology LFT-VI speakers, which are wonderfully open and throw a big soundstage but need some low end augmentation. I would like to get the low end down to about 30 Hz realistically for such a small sub.

An Infraplanar sub would be ideal, but I don't want to spend tripple the entire system cost for a sub. Not going to put that kind of money into a second system.